The present disclosure relates in general to valve timing control apparatuses, and in particular to variable valve timing control apparatuses for internal combustion engines. The valve timing control apparatus controls a relative rotation between a camshaft and an output shaft, which can either be prevented or permitted by releasably locking a relative rotation of a rotor being driven by said camshaft with a rotational member, preferably a sprocket, a chain, a belt, a pulley being driven by said output shaft.
From the state of the art a cam phasing device as part of a variable valve timing control apparatus is well known that is applicable to internal combustion engines, such as described in U.S. Pat. No. 7,841,311 B. Especially with camshafts that include adjustable cams for intake and exhaust gas exchange valves of cylinders of a combustion engine on the same camshaft, a cam phaser device may be needed. Any kind of camshaft can be operated that has one or two different sets of cams, whereby the cams can be arranged on the same camshaft or on different camshafts. The device is applicable in an automotive environment as an automotive component.
A variable valve timing control apparatus of an internal combustion engine is a device that adapts the relative position of a gas exchange valve actuating component, such as a cam, with respect to a further shaft, such as a crankshaft. It is widely known to use camshafts for transmitting the actuating impulse. The impulse is applicable on at least one—normally several—gas exchange valves via a control shaft. The control shaft can have at least two concentrically arranged camshafts, or can have two separate camshafts arranged in parallel. The camshafts are adjustable in a rotatable manner with respect to a rotational member, e.g., a sprocket, a toothed belt, a pulley or a gear assembly, which is powered by the engine's rotational movement. The adjustment is achieved by adjusting a cam of the first camshaft in terms of its angle towards a cam of the second camshaft. To select the position, a cam phasing device is needed. The cam phasing device operates by rotatable vanes which are part of a rotor, provoking a swiveling relative movement between a driven member and an output member, which can be a rotor connected with a camshaft for opening and closing cylinder valves of the combustion engine.
The rotor's vanes can be profiled or can be flat, three-dimensional blocks extending out of the central rotor which can be referred to as rotor cores. The central rotor and the vanes are part of a vane adjuster. The cam phasing device can include at least two pivotable vane adjusters. Each pivotable vane adjuster is assigned to one of the two camshafts. In particular, a first vane adjuster is fixed to a first camshaft and a second vane adjuster is fixed to a second camshaft. The first vane adjuster operates the first camshaft whereas the second vane adjuster operates the second camshaft. The pivotable vane adjusters can be arranged axially one after the other in a direction of a valve control shaft. Both vane adjusters can be arranged on a common axis or can be arranged on parallel axes. The vane adjusters usually do not influence each other in their maximum swivel range. The first vane adjuster may still cover its full range while the second vane adjuster has picked any position between its maximum advanced and its maximum retarded position. With this design, the position of a first camshaft does not influence the selectability of a position for the second camshaft still occupying the same elongated space.
The variable valve timing control apparatus can further include rotor-type vane adjusters in that each pivotable vane adjuster is designed in a rotor-type manner. Each rotor-type vane adjuster can be changed in respect of its phase by hydraulic pressure in two sets of hydraulic chambers, which can provide a retard and an advance region of the valve timing control apparatus. The phase is measured in respect of a further shaft, such as the camshaft. The two sets of hydraulic chambers—retard and advance regions—form counter moving chambers to each other. The pivotable vane adjusters each constitute an output member of one of the camshafts. Each output member includes a vane rim. The vane rims are attached to rotor cores being movable between a first position and a second position limited by division bars of a surrounding stator housing. By using the design of vane-type cam phasers—which are known to a certain extent by themselves—a very fast and very responsive adjuster can be created.
In some cases, the variable valve timing control apparatus can include a double camshaft. The gas exchange valve control shaft is thereby a coaxially arranged double camshaft. The first camshaft can be formed of said double camshaft as a hollow body and the second camshaft is aligned in the hollow body and is placed in such a manner that through at least one recess a cam of the second camshaft pokes out to an outside of the first camshaft. The double camshaft is very efficient in terms of space. It occupies very little additional space outside of the camshaft as is necessary and advantageous in internal combustion engines.
Frequently, the variable valve timing control apparatus has only one drive pulley. The drive pulley is exposed to a driving means, such as a chain or a belt. Thus the cam phasing device has only one drive pulley, such as a sprocket, a toothed belt, a pulley, a gear box, etc., adapted to be driven by a chain which can surround a crankshaft of the internal combustion engine. The variable valve timing control apparatus has a side which is a near side of the camshaft, and the variable valve timing control apparatus has a side which is a far side from the camshaft. The variable valve timing control apparatus can be planar. The variable valve timing control apparatus has a communication collar on the near side. The near side bears conduits for intake and piping of a hydraulic fluid to each of the sets of chambers of the first and said second pivotable vane adjusters. The communication collar moves synchronously along with the drive pulley. The integration of hydraulic conduits for the first and second vane adjusters can contribute to the compactness of the variable valve timing control apparatus. The same applies to using only one drive pulley. The variable valve timing control apparatus has at least four conduits. Two of the four conduits are located in the vicinity of an axis of the camshaft which channel fluid from the communication collar to the pivotable vane adjuster. They conduct hydraulic fluid, such as engine oil, to the vane adjuster which is located farther away from the communication collar than the second pivotable vane adjuster. The two of the four conduits are located remotely from the axis of the camshaft channel from the communication collar to the second pivotable vane adjuster. The second vane adjuster is located closer to the communication collar. In a very dense circular cross-section, all conduits necessary for operation can be placed in the rotor core and the core of the variable valve timing control apparatus.
It is an object to further improve the above-described valve timing control apparatus.